1. Field of the Invention
The present invention relates to combined boards and methods for manufacturing the same. More particularly, the present invention relates to combined boards, e.g., vehicle trims, that comprise two substrates that are arranged to form an overlap portion and connected to each other in the overlap portion, and methods for manufacturing the same.
2. Description of the Related Art
A method for manufacturing a combined board is taught, for example, by Japanese Laid-open Patent Publication Number 11-208271, in which a vehicle trim is exemplified as the combined board. In this known art, the vehicle trim comprises first and second trim substrates made from a synthetic resin. The first (lower) trim substrate integrally includes a projection or pin that extends from its inner surface. On the other hand, the second (upper) trim substrate is formed with an aperture that is adapted to receive the pin when the first and second trim substrates are partly overlapped. The first and second trim substrates thus constructed are arranged to form an overlap portion and the pin of the first trim substrate is inserted into the aperture of the second trim substrate. Thereafter, the pin is heated from an inner side of the second trim substrate in order to melt its projecting end, thereby forming a caulked joint portion in the overlap portion. As a result, these trim substrates are connected to each other in the overlap portion, thereby producing the vehicle trim.
However, because the pin of the first trim substrate is not bonded to the aperture of the second trim substrate, the caulked joint portion in this known method may lack connecting force. In addition, such a caulked joint portion may produce looseness on the joint portion. As a result, the trim substrates cannot be desirably or sufficiently connected each other. Such insufficient connection may lead to inferior quality of the produced combined board.
In another known method for manufacturing a combined board, two substrates are arranged to form an overlap portion and are simply adhered to each other in the overlap portion by utilizing adhesives, thereby forming a combined board.
However, this known technique typically increases costs for manufacturing the combined board, because the adhesives are relatively expensive. In addition, labor-intensive and time consuming work is required to form the combined board, because relatively long time is required for the adhesives to completely set.